This research project will establish a non-invasive biomonitoring capability to evaluate exposure to organophosphorus (OP) insecticides utilizing a sensitive, non-invasive, micro-analytical instrument for realtime analysis of biomarkers of exposure and response in saliva. This project will create a miniaturized nanobioelectronic biosensor that is highly selective and sensitive for the target analyte(s). In addition, a physiologically based pharmacokinetic and pharmacodynamic model (PBPK/PD) for the OP insecticide chlorpyrifos will be modified to incorporate a salivary gland compartment that will be used to quantitatively predict blood chlorpyrifos concentration and saliva cholinesterase (ChE) inhibition to estimate exposure based on a saliva specimen. The utilization of saliva for biomonitoring, coupled to real-time monitoring and modeling is a novel approach with broad application for evaluating occupational exposures to insecticides. An OP sensor will be developed based on a new biosensing principle of antigen-induced formation of nanoparticle-immuno complex nanostructure. A ChE sensor will also be developed based on the electrodetection of the ChE hydrolyzed reaction products choline and hydrogen peroxide. Subsequently, the sensors will be transformed to a "lab-on-a-chip", and the biochip performance will be characterized, optimized and validated. To validate this approach the pharmacokinetics of chlorpyrifos excretion and ChE inhibition in saliva under various physiological conditions and dose levels will be assessed to ensure that these endpoints are accurate predictors of internal dose. The development of a real-time saliva analysis coupled to a predictive pharmacokinetic model represents a significant advancement over current biomonitoring strategies. Once this model system has been adequately validated it can readily be employed to assess worker exposure to insecticides under a wide range of occupational situations.